596 POSKTSCRIPT. 



Divine progress in the creations attributed, — "if one new 

 one were to be every year called into being," — is assumed 

 by the great geologist only for the sake of argumentative 

 illustration, and not as the actual or even hypothetical 

 rate of successive creation and extinction of species. But 

 the principle remains the same, whether the rate assumed 

 is one a daj^ or one a year, or one a century. 



It is conceived that the arguments of Lyell will not be 

 unfairly represented in the following postulates : — 1. One 

 new species of animal or plant might have been created 

 yearly, and one old species might have been extinguished 

 yearly, without mankind having become aware of these 

 events. — 2. Such a rate of change would have been ade- 

 quate to effect the displacements and replacements of 

 species, between times past and times present, which are 

 discovered by geologic researches. — 3. New creations of 

 distinct species in each case afford the more probable 

 explanation of the mode of change, because we do not 

 detect any present mutation of species, such as can be 

 deemed adequate to account for the geologipo- historical 

 facts ascertained. 



Let that rate of change in the flora or fauna of the 

 earth be argumentatively admitted as true ; namely, one 

 a year. And let the expressions ' ten million ' and ' ten 

 thousand ' be employed to designate large un-counted 

 numbers. Lyell's arguments may then be met by 

 counter postulates, quite as plausible in themselves, and 

 more in accordance with known facts, than is the idea of 

 so many sudden creations of unchanging species, distinct 

 from first to last. 



1. The typical form of any species is the standard or 

 average of the ten million individuals which represent it 

 at any date. — 2. Each year ten thousand species may 

 possibly be undergoing an excessively minute change in 



